I have to excuse myself I am not an abhidhamma-scholar even though I would like to learn more about it. In what way does the Patthana provide solutions to the problems pointed out by Waldron? I am by the way not very found of american scholarship simply out of the reason of the sometimes low quality of the philological base of their research, and I would not be too surprised to see that Waldron's publication suffer the same shortcomings. Mainly for the reason that he did publish a very euphoric review of a publication of Dan Lusthaus which I, after going through it with some care, have to dismiss as quite weak when it comes to the understanding of the used source languages.
But this has in my eyes nothing to do with the research subject (mahāyāna buddhism), but rather with the specific climate of the universities. Japanese and continental european scholars usually pay much more attention to the philological base and are also less prone to philosophic speculation, which in my eyes is the way to go.

SarathW wrote:The question I have is whether Arahant also possess Bhavanga Citta.

Probably, as the Arahant's living, post-awakening, no longer generates kamma, but is still subject to the kamma already flowing through it.

Bhavangacitta, AFAIK, is similar to "temperament", a factor of constitution, in the sense of inborn, innate tendencies; and as distinct from (1) emotions, which are complex social-culturally conditioned mental constructs (sankhara), and (2) moods, more like temporary inclinations.

Mhhmmm. I think there are still aspects of the bhavaṅgacitta that need to be understood properly and I reach the limits of my mental capability when I try to make the abhidhammic model work for me. Maybe there is something that I fundamentally got wrong, and certainly my understanding of pāli abhidhamma is yet poor and relying on the secondary sources (here mainly Bhikkhu Bodhi, Gethin's article and a chapter in Paul Griffiths Mind-Body Problem) is not entirely satisfying. But on the other hand I do at the moment not have the time to dive seriously into pāli abhidhamma, even though that would be the appropiate move.

According to Bhikkhu Bodhi's definition that was quoted in this thread earlier, I suspect that bhavaṅgacitta in his interpretation is occuring within a strictly momentary concept of mind-phenomena, right? So there can either be bhavaṅgacitta, or active cognition, but not both at the same time.
To quote his precise words once again:

When an object impinges on a sense door, the bhavanga is arrested
and an active cognitive process ensues for the purpose of cognizing the
object. Immediately after the cognitive process is completed, again the
bhavanga supervenes and continues until the next cognitive process
arises.

I therefore assume that from Bhikkhu Bodhis interpretation, no multilayered, or at least double-layered model of consciousness can be applied. A double-layered-consciousness model would be the minimum prerequisite in order to talk about 'consciousness' and 'subconsciousness' in the way that modern psychology understands it.
Now such a division is done by Nyanatiloka when he describes the bhavaṅga-citta thus:

is in the Abhidhamma commentaries explained as the foundation or
condition (kāraṇa) of existence (bhava), as the sine qua non of life, and
that in form of a process, lit. a ‘flux’ or ‘stream’ (sota), in which since
time immemorial all impressions and experiences are, as it were, stored
up, or better said functioning, but as such concealed to full consciousness,
from where however they as subconscious phenomena occasionally
emerge and approach the threshold of full consciousness, or crossing it
become fully conscious. This so-called ‘subconscious life-stream’ or
undercurrent of life, which certain modern psychologists call the
Unconscious or the soul, is that by which might be explained the fac-
ulty of memory, the problem of telekinesis, mental and physical growth,
karma and rebirth, etc.

Gethin accused Nyanatiloka at this point for 'entering the realm of creative Buddhist psychology', as Nyanatiloka's interpretation cannot be supported by the ancient scriptures, and there are a few other writer who would agree to this position.

Now Gethin at another place comes to this conclusion:

A being’s bhavaṅga is of the same type throughout his or her life—this is, of course, just another way of saying that it is the
bhavaṅga that defines the kind of being. It follows that the only time the nature of a
being’s bhavaṅga can change is during the process of death and rebirth. So how does it
come about that a being’s bhavaṅga is of such and such a kind and not another?

And furthermore:

The fact that the Abhidhamma uses the notion of bhavaṅga to define both the
nature of a given being and also what constitutes a lifetime as that being suggests that
bhavaṅga is being used to explain not merely the logic of continuity but also why a
particular being continues to be that particular being throughout his or her life, rather than
becoming some other being—to become another being is to change one’s bhavaṅga.
Thus, why I do not suddenly start behaving like an animal is because I have what is
essentially a human bhavaṅga. In other words, the notion of bhavaṅga is, in part at least,
intended to provide some account of why I am me and why I continue to behave like me;
it is surely intended to give some theoretical basis for observed consistency in behaviour
patterns, character traits and the habitual mental states of a given individual.

In a strict momentary, one-layered consciousness-model it is hard to account for the fact that the bhavaṅga defines what somebody is, while at the same time it does not exists continuously. Obviously, the abhidharmic way to explain this phenomena is lacking some 'flesh on the bone'. As Bhikkhu Bodhi was quoted above, bhavaṅgacitta is a state of mind to which the mind returns after there was an active process of cognition. So when this state of mind defines the characteristics of the human being, where does this information get stored when there is an active process of cognition?
This problem is recognized by Gethin:

This brings one up against one of the basic problems of Buddhist thought. If consciousness is understood to consist of a
temporal series of consciousness moments each having an individual object, then when
an ordinary being (puthujjana) is experiencing wholesome consciousness, what at that
moment distinguishes him or her from an arahant? In other words, in what sense do the
unwholesome tendencies and defilements still exist for that being? The answer is, of
course, in the sense that they might arise at any moment. That is to say, they exist
potentially. But where—or perhaps how—do they exist potentially? This is clearly a
problem that historically Buddhist thought was well aware of.

his conclusion therefore is:

I hope to have shown in this paper that bhavaṅga is most
definitely not to be understood merely as a kind of “mental blank” and “logical stop-
gap”. For any given being bhavaṅga consciousness represents a mental province where at
least certain characteristics unique to that individual are located (although the spatial
metaphor is not the one preferred by the texts). Moreover this mental province exercises a certain determinative
power over conscious mental states. While it is perhaps something of a misconceived
exercise to speculate on whether this understanding of bhavaṅga had a direct and explicit
influence on the development of the Yogācārin notion of the ālaya-vijñāna, it surely must
be the case that these two concepts are to be understood as having a certain affinity and
that they belong to the same complex of ideas within the history of Buddhist thought.

Gethin hints here in a direction that we might have to understand the consciousness-model of the abhidhamma more in a two-layered fashion than it has been done by research and tradition so far. If it is more than just a gap-filler, but a mental sphere that stores certain characteristics of a human being, this mental sphere needs to be able to coexist with the current active cognition process. This is strongly hinted at by

as elaborated in the Paṭṭhāna, the bhavaṅga state of mind must be understood as conditioning in various ways a being’s every
response to the world around him or her. Although passive in so far as it is a vipāka, the
bhavaṅga mind, like all dhammas and assemblages of dhammas, will inevitably
condition other dhammas and assemblages of dhammas by way of certain of the twenty-
four conditional relations. There is a sense then in which the bhavaṅga can be seen as a
deeper level of the mind that acts on our conscious mind. Ordinary waking experience is
thus presented in the Abhidhamma as a kind of dialogue between one’s essential nature
(bhavaṅga) and various external stimuli. However, even reference to the intricacies of the
Paṭṭhāna is unlikely to answer all our questions.

Of course nowhere in the Paṭṭhāna is actually a two-layered model presented. Two-layered consciousness here is only possible insofar as there can be bhavaṅga or active cognition in different kṣanas/moments, but not within the same. This is certainly in accordance with the observations about the teaching of momentariness in the Theravāda-tradition given by von Rospatt (pages 32-34 of: The Buddhist doctrine of momentariness: a survey of the origins and early phase of this doctrine up to Vasubandhu. By Alexander von Rospatt. (Alt–und Neu–Indische Studien hrsg.vom Institut fur Kultur und Geschichte Indiens und Tibets an der Universitat Hamburg, Band 47.) pp. x, 285. Stuttgart, Franz Steiner Verlag, 1995.)

For a full working ālaya-vijñāna-concept, there can be no doubt that at least two levels of consciousness need to be accepted (this is true even for the sautrāntrika-compatible concept of ālaya-vijñāna put forward by Vasubandhu in the Karmasiddhiprakaraṇa; for a discussion see: Schmithausen, L. “Sautrāntika-Vorausetzungen in Viṃśatikā und Triṃśikā.” Edited by E. Frauwallner & G. Oberhammer. Wiener Zeitschrift für die Kunde Süd- und Ostasiens (Wien) XI (1967): 109–250.) Later yogācāra-interpretation gives up to eight concurrent conciousnesses, but for the sake of simplicity the dual model of the Karmasiddhiprakaraṇa already suffices to account for continuity as an underlying stream of consciousness is accepted.

In accordance to Gethin's observations, it is therefore not surprising that Vasubandhu chooses the bhavaṅga-citta of the Theravādins (in the tibetan and chinese rendering without any doubt a clear translation of bhavaṅga: "srid pa'i yan lag gi rnam par shes pa" and translated by Xuanzang as 有分識) as the point of reference for his teaching of ālaya-vijñāna towards his sautrāntika-companions.

Now Xuanzang can give further clarity on this very clear mahāyānistic interpretation of the bhavaṅga-citta:

In the Sutras of the Theravādins and the Vibhajyavādins, [the ālayāvijñāna] is called in a hidden way 'bhavaṅga-citta'.
'bhava' in this case means the threefold existence, and 'aṅga' has the meaning of 'cause'. This eternal universally existing thing can only be ālayāvijñāna, and only this can be threefold existence and the cause.
上座部經分別論者，俱密意說此名「有分識」。
「有」謂三有，「分」是因義 ，唯此恒遍，為三有因。

Kuiji is certainly nice to give some further explanations to the analogies between bhavaṅga-citta and ālayavijñāna:

The nature [of bhavaṅga-citta] is eternal and not cut-off. It pervades universally the three realms. It it the three existences and the cause.
The other six types of [ordinary] consciousness [five sense-organs + mind] are cut-off with respect to time, because they are not universally pervading.
Therefore, these six types of [ordinary] consciousness are different from the bhavaṇga-citta. This is not mentioned by Vasubandhu in the Mahāyāna-saṃgrāha.
體恒不斷。周遍三界。為三有因。其餘六識時間斷故。有不遍故。故非有分。

Now Xuanzang, Kuiji and on the indian side Asvabhāva simply solve this problem by describing bhavaṇga as a 方便 /upāya-kauśalya of ālayavijñāna and that's it. For them it is obviously that the bhavaṇga must exist continually, concurrent with active cognition and is thus not a slave to momentariness and the idea that it exists only after any cognition has ceased/before a new cognition has arisen, but not in a continuous manner.

If im not entirely mistaken in my procedure, I come to the personal conclusion that the bhavaṅga-citta within the Theravāda-thoughtworld is a move into the direction of finding a solution for the 'continuity vs. momentariness'-problem, yet it lacks some key points in order to prove a solution to the problem. The question whether Vasubandhu developed his understanding of ālayavijñāna based on the concept of bhavaṅga remains open, but personally I think it is not necessarily the case. I rather believe that Vasubandhu did see the bhavaṅga-citta as a 'weak spot' in the Theravāda-Abhidhamma and used it as an entry point to introduce his own new concept, which, from the bird's perspective might appear as if it could be a continual development, but in fact is unlikely to be one, since the concept of ālayavijñāna is not linked to bhavaṅga-citta in the earliest occurences of the concept ālayavijñāna.
I have the impression that the only genuine equation of ālayavijñāna and bhavaṅga-citta has been done by Vasubandhu in the Karmasiddhiprakaraṇa, and later generations of writers and commentators just repeated this statement of Vasubandhu at the appropiate places.

Above message maybe out of date. Latest update will be in massage's link.--------------------------------------------------
Tipitaka memorization is a rule of monks. It isn't just a choice. They must done it.
bahussuto nāma tividho hoti – nissayamuccanako, parisupaṭṭhāpako, bhikkhunovādakoti. http://UnmixedTheravada.blogspot.com/20 ... monks.html